Effect of Embodied Energy on Cost-Effectiveness of A

Article Eﬀect of Embodied Energy on Cost-Eﬀectiveness of a Prefabricated Modular Solution on Renovation Scenarios in Social Housing in Porto, Portugal

Manuela Almeida , Ricardo Barbosa * and Raphaele Malheiro

Department of Civil Engineering, University of Minho, 4800-058 Guimarães, Portugal; [email protected] (M.A.); [email protected] (R.M.) * Correspondence: [email protected]; Tel.: +351-253-510-200

Received: 2 December 2019; Accepted: 17 February 2020; Published: 21 February 2020

Abstract: A large-scale energy renovation intervention in existing buildings has been consistently presented as the most significant opportunity to contribute to achieving the European targets for 2030 and 2050. One of the key points for such achievement is the cost-effectiveness of the interventions proposed, which is also closely related to decent housing affordability. Prefabricated modular solutions have been pointed out as a pathway, but there are knowledge gaps regarding both its cost-effectiveness and its environmental performance. Considering a social housing multi-family building in Porto, Portugal, as a case study, this research employs energy simulations, a cost-optimal methodology and a life cycle analysis approach to assess the influence of considering embodied energy and emissions in cost-effectiveness calculations. In general terms, the hierarchical relation between calculated renovation scenarios remain identical, as well as the choice of the cost-optimal combination, which can reduce primary energy needs by 226 kWh/(y.m2). However, embodied carbon emissions and embodied energy of the materials used in the calculations, which are indicative of the sustainability of such interventions, increase the energy and carbon emissions associated to each 2 2 renovation package by an average of 43 kWh/(y.m ) and 9.3 kgCO2eq/(y.m ), respectively.

Keywords: modular; prefabricated; renovation panel; energy renovation; cost-eﬀectiveness; embodied energy; social housing

1. Introduction Cities hold significant responsibility in terms of energy and resources consumption. Urban areas, which accommodate more than half of the global population, consume up to 80% of global material and energy supplies and produce around 75% of the carbon emissions worldwide [1]. The countries belonging to the Organization for Economic Cooperation and Development (OCDE), for example, emitted 9.6 tons of CO2 per capita on average in 2013, solely from fossil fuel combustion. The latest data from OCDE also indicated that emissions per capita ranged from 4 to 18 tons per person in 2015 and that in Portugal these emissions were close to 4 tons per person in that year [2]. Buildings are accountable for a determinant share on carbon emissions, in particular, related with energy consumption [3], and there is strong evidence that improving the energy efficiency of the existing built environment is one of the most effective ways to achieve the ambitious goals that European Union (EU) established for 2050 [4]. The EU has set environmental and energy targets to be achieved by 2030 and by 2050 to reach a more competitive, safe and low carbon economy [4,5]. Regarding the building sector and within the regulatory initiatives elaborated in this context, the Energy Performance of Buildings Directive (EPBD), and in particular, its recast in 2010, can be considered a turning point where new game-changing

Sustainability 2020, 12, 1631; doi:10.3390/su12041631 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 1631 2 of 17 concepts were introduced, such as the nearly Zero-Energy Buildings (nZEB) [6], which are characterized by a high energy performance. The nearly zero or very low amount of energy required in these buildings must be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby [6]. Notably, according to this directive, Member States should ensure that from 31 December 2020, all new buildings are built as nZEB [6]. Although this timeline is considered to be determinant for the achievement of the EU targets, many of the current policies still have their main focus on new buildings, which some studies indicate as not being sufficient. The majority of the European building stock has more than twenty years old and present low energy performance [7]. Considering the significant energy reductions that can be achieved by cost-effective energy renovations and that the replacement rate of existing buildings by new buildings is only around 1% to 2% per year [8], there is significant potential for decarbonization of the building stock. To unlock this potential, it is necessary to promote a large-scale energy renovation throughout Europe. There are, however, significant and well-known barriers to overcome [9]. One of the most mentioned barriers concerns the cost of interventions, which is closely linked to the concept of housing affordability [10]. Cities of today are under different kind of constant pressures, such as gentrification and speculation in the housing prices, and some authors argue for the urgent need to guarantee affordable housing [11]. The question of affordability is also determinant for reasons of energy poverty alleviation, in particular, when sensitive contexts are in place, such as in the case of renovation of social housing buildings [12]. In this context, there is a growing trend concerning the exploration of new solutions that can provide economic advantages in comparison with the conventional renovation solutions, which are already well implemented in the construction sector. One of the directions pointed out by a significant number of research studies is the use and implementation of modular prefabrication construction technology and techniques, which presents significant potential in economic, environmental, energy and material terms. Solutions produced in industrial assembly lines are potentially more accessible because the process is easily replicable, and the procurement of raw materials is higher, resulting in lower costs and greater economies of scale. The simplification of the assembly process of prefabricated solutions substantially reduces the time of application in the building and the construction waste. Furthermore, the prefabrication of renovation solutions guarantees greater quality control [13]. Although the modular prefabricated solutions for building renovation have been approached from distinctive perspectives in previous research studies (e.g., Reference [14]), in particular, in Northern Europe countries, there is a limited number of studies concerning implementation in southern Europe, where this kind of solutions are usually directed for new construction of industrial and office buildings. In addition, there is an important gap in knowledge about the environmental performance of this type of solution, but there is evidence in the literature that points out positive environmental outcomes [15]. The environmental performance of the existing buildings is directly related to the materials that are added to the building and with the energy that is spent in the process. Thus, although the impact of a building renovation would be smaller when compared to the construction of new buildings where larger amounts of materials are involved [16], the type of solution adopted is determinant for its environmental performance. In this sense, this paper investigates the influence of the embodied energy and embodied carbon emissions on the cost-effectiveness of several renovation scenarios in a southern European context, compiling different solutions, including a modular prefabricated panel developed in the University of Minho in a framework of a European research project designated as MORE-CONNECT. Using a social housing multi-family building located in Porto, Portugal, as a case study, the methodology employs energy simulations and intends to balance the primary energy demand and the global costs of each renovation scenario, to compare them using a life cycle approach, which differs from the common approach that focus only on energy during the operation phase [17]. The methodology used in this study is presented in Section2. Section3 describes the case study building. Sustainability 2020, 12, 1631 3 of 17

Results from the analysis are presented and discussed in Section4. Finally, conclusions are presented in Section5.

2. Methodology With the objective of comparing the eﬀects of embodied energy and the carbon emissions on the cost-eﬀectiveness of renovation scenarios, the methodologic framework used in this study comprises a two-step approach: A cost optimal methodology and a life cycle assessment, both described in the next two sub-sections.

2.1. Cost-Optimal Methodology The procedure used in this study is in line with the cost-optimal calculations methodology indicated by the EU Delegated Regulation No. 244/2012 [18] as a complement to the recast of the Energy Performance of Buildings Directive (EPBD-recast) [6]. The first step of the methodological framework is the cost-optimal methodology, which is based on the comparison of several renovation scenarios with a reference case, composed of what has been designated as “anyway renovation” measures. The “anyway renovation” measures constitute a renovation intervention where the energy performance of the building is not improved, just dealing with aesthetical, functional and structural issues. This reference case is also useful to establish the threshold for the cost-effectiveness of renovation scenarios. If a renovation scenario presents a lower energy demand and lower costs than the reference case, it is considered cost-effective. The renovation scenarios consist of packages of renovation measures that include improvements in the building envelope and in the Building Integrated Technical Systems (BITS), such as an air-conditioning system or a gas boiler, together with the inclusion of renewable energy sources. The comparison between the renovation scenarios requires the calculation of the energy use related to each of them, as well as the calculation of the related carbon emissions and global costs. According to this methodology, the method for energy calculation should be chosen in accordance with local thermal regulations, given the existing diversity of climate conditions and construction characteristics. In this study, building energy performance calculations were based on the quasi-steady-state method officially prescribed in the Portuguese legislation [19]. This method is widely used in Portugal and results can be used as a benchmark for comparison with other studies in the same context. Detailed data regarding real energy consumptions for heating and cooling is not available at this scale. For calculations regarding renewable energy supply sources, SCE.ER [20], and PVGIS [21] were used. The global costs calculation used was based on the current market reference prices [22], and includes all costs, namely, investment costs, maintenance costs, energy costs, replacement and disposal at the end of the calculation period. The costs assessment considered not only the materials and systems involved in the interventions, but also preparatory works (such as scaffolding) and man-hour costs. Although the focus of the study is on the methodological approach, the use of established methods for assessing energy and costs was considered important to increase the level of confidence in the results. The calculations considered a life cycle of 30 years, in line with the previously cited EU Delegated Regulation methodology. In order to take into account future costs, the methodology follows the annuity method. The annuity method is favorable in the case of parametric cost assessments of various packages of renovation measures. By using the annuity method described in another study [23], it is not necessary to determine residual values at the end of a present assessment period for measures, which have a longer life than the assumed time horizon of the cost assessment. This way, it allows obtaining average yearly values for measures with different service lives. The results of the comparison of the different renovation packages can be illustrated with the help of graphs, where the x-axis presents the primary energy use and the y-axis presents the global costs (Figure1). Sustainability 2020, 12, 1631 4 of 17 Sustainability 2020, 12, x FOR PEER REVIEW 4 of 17

Figure 1.Figure Cost-effectiveness 1. Cost-effectiveness threshold threshold andand identification identification of the cost-optimalof the cost-optimal renovation scenario. renovation Source: scenario. Adapted from Reference [24]. Source: Adapted from Reference [24]. 2.2. Life Cycle Assessment 2.2. Life CycleIn Assessment this study, a Life Cycle Analysis (LCA) approach was used to expand the cost-optimal In thismethodology. study, a The Life methods Cycle used Analysis in this study (LCA) concerning approach the LCA was analysis usedare todetailed expand in thethe Annex cost-optimal 56 report – Life Cycle Assessment methodology for energy-related building renovation [16]. methodology.The The LCA methods methodology used is in used this to study quantify conc theerning embodied the primary LCA analysis energy and are embodied detailed carbon in the Annex 56 reportemissions – Life Cycle concerning Assessment the manufacturing, methodology replacement for energy-related and end-of-life building of construction renovation materials [16]. and TheBITS LCA added methodology during a building is used renovation to quantify [16]. Many the indicatorsembodied have primary been developed energy in and LCA, embodied describing carbon emissionsenvironmental concerning impacts, the manufacturing, resource use or replacemen additional environmentalt and end-of-life information. of construction However, frommaterials a and BITS addedpractical during point ofa building view, the numberrenovation of indicators [16]. Many in this studyindicators has been have limited been to three:developed Carbon in LCA, emissions represented by the global warming potential (quantifying the amount of CO2 involved in each describingrenovation environmental package), cumulativeimpacts, resource Non-Renewable use or Primary additional Energy environmental (NRPE) demand information. and cumulative However, from a practicaltotal primary point energy of view, demand the [number16]. of indicators in this study has been limited to three: Carbon emissions representedTo perform aby LCA the analysis, global itwarming is fundamental potential to define (quantifying two types ofthe system amount boundaries: of CO2 Theinvolved in each renovationtemporal boundary package), (defining cumulative elementary Non- stages,Renewable occurring during Primary the life ofEnergy the building), (NRPE) which demand was and cumulativedefined total according primary to ENenergy 15978 demand standard [[16].25], and the physical boundary (where materials and energy flows are defined). The focus of the analysis is on energy-related measures applied in buildings, and To therefore,perform thea LCA LCA assessmentanalysis, onlyit is tookfundamental into account to measures define thattwo a fftypesect their of energy system performance boundaries: The temporal(thermal boundary envelope, (defining building elementary integrated technicalstages, occu systemsrring and during energy the use forlife on-site of the production building), and which was defined accordingdelivered energy). to EN To 15978 assess standard the impact [25], of the and renovation the physical scenarios boundary analyzed in (where this study, materials the number and energy flows areof defined). materials involved The focus was of calculated the analysis for each is measureon energy-related and was multiplied measures by the applied related impactsin buildings, in and therefore, the LCA assessment only took into account measures that affect their energy performance (thermal envelope, building integrated technical systems and energy use for on-site production and delivered energy). To assess the impact of the renovation scenarios analyzed in this study, the number of materials involved was calculated for each measure and was multiplied by the related impacts in terms of embodied energy and carbon emissions (by energy carrier). Results are expressed per unit of surface area per year after dividing the LCA results for the reference study of the building (30 years). The LCA for building renovation, taking into account materials and BITS, as well as the operational primary energy use, was calculated according to Equation (1) [16]. =++ PEbuilding PE materials PE BITS PE op energy use (1) Sustainability 2020, 12, 1631 5 of 17

terms of embodied energy and carbon emissions (by energy carrier). Results are expressed per unit of surface area per year after dividing the LCA results for the reference study of the building (30 years). The LCA for building renovation, taking into account materials and BITS, as well as the operational primary energy use, was calculated according to Equation (1) [16]. Sustainability 2020, 12, x FOR PEER REVIEW 5 of 17 PEbuilding = PEmaterials + PEBITS + PEop energy use (1) where PEbuilding is the primary energy associated to the building renovation, PEmaterials is the primary energywhere PEassociatedbuilding is to the all primary materials energy which associated were used to in the the building building renovation, renovation, PE materialsPEBITS isis the the primary primary energyenergy associated associated to to the all materialsBITS, and which PEop energy were use usedis the in calculated the building primary renovation, energy PE forBITS theis operational the primary energyenergy use. associated The same to the logic BITS, applied and PE toop Equation energy use is(1 the) is calculatedused for the primary carbon energy emissions for the calculations. operational Furthermore,energy use. for The the same purpose logic of applied differentiating to Equation the primary (1) is used energy for the demand carbon (and emissions carbon calculations.emissions), whichFurthermore, consider for the the different purpose stages of di ffinerentiating the building the life primary cycle, energythe terms demand “embodied (and carbonprimary emissions), energy” andwhich “embodied consider carbon the diff emissions”erent stages were in the applied. building The life assessment cycle, the termsused an “embodied LCA database primary developed energy” forand the “embodied Portuguese carbon context emissions” [26]. were applied. The assessment used an LCA database developed for the Portuguese context [26]. 3. Case Study Building and Renovation Scenarios 3. Case Study Building and Renovation Scenarios 3.1. Definition of the Case Study Building 3.1. Definition of the Case Study Building The case study used in this research is a social housing building, built in 1997 (Figure 2). It is The case study used in this research is a social housing building, built in 1997 (Figure2). It is managed by the municipal company GAIURB, and it is considered to be representative of the type of managed by the municipal company GAIURB, and it is considered to be representative of the type of construction of the national building stock of multi-family buildings built between 1991 and 2012. construction of the national building stock of multi-family buildings built between 1991 and 2012. This This type of construction represents around 40% of the multi-family buildings in Portugal [27]. type of construction represents around 40% of the multi-family buildings in Portugal [27].

(a) (b)

Figure 2. Main (a) and back (b) façades of the pilot building in Vila Nova de Gaia, Portugal. Figure 2. Main (a) and back (b) façades of the pilot building in Vila Nova de Gaia, Portugal. The building is situated in, Porto Metropolitan Area, in the north region of Portugal. The location The building is situated in, Porto Metropolitan Area, in the north region of Portugal. The location of the building is classified as Csb (Mediterranean warm/cool summer climates) in the Köppen and of the building is classified as Csb (Mediterranean warm/cool summer climates) in the Köppen and Geiger climate system. The average annual temperature is 14.4 C with the hottest month being August Geiger climate system. The average annual temperature is 14.4◦ °C with the hottest month being (average of 19.6 C) and January being the coldest with an average of 9.1 C[28]. August (average ◦of 19.6 °C) and January being the coldest with an average◦ of 9.1 °C [28]. The building has a predominant west–east orientation. It has three separate entrances, each The building has a predominant west–east orientation. It has three separate entrances, each giving access to three floors and corresponding to six apartments (a two-bedroom apartment and a giving access to three floors and corresponding to six apartments (a two-bedroom apartment and a three-bedroom apartment per floor). In total, the building has eighteen apartments. Aluminum frame three-bedroom apartment per floor). In total, the building has eighteen apartments. Aluminum frame windows with double-glazing, pitched roof with ceramic tiles (3 cm of insulation) and double pane windows with double-glazing, pitched roof with ceramic tiles (3 cm of insulation) and double pane masonry walls without thermal insulation constitute the building envelope. The domestic hot water is masonry walls without thermal insulation constitute the building envelope. The domestic hot water provided through a gas heater available in each apartment, and there is no central heating or cooling is provided through a gas heater available in each apartment, and there is no central heating or system installed in the building. cooling system installed in the building. Table 1 characterizes the main building areas, and Table 2 presents the most important energy parameters of the pilot building. Calculated energy needs and primary energy for the existing situation clearly indicate a low energy efficiency and the need for intervention. The energy needs correspond to the energy needed to achieve a certain level of comfort temperatures, and the primary energy is the energy as found in nature, and unlike the energy needs, take into consideration equipment efficiency and conversion factors from the energy sources used.

Sustainability 2020, 12, 1631 6 of 17

Table1 characterizes the main building areas, and Table2 presents the most important energy parameters of the pilot building. Calculated energy needs and primary energy for the existing situation clearly indicate a low energy eﬃciency and the need for intervention. The energy needs correspond to the energy needed to achieve a certain level of comfort temperatures, and the primary energy is the energy as found in nature, and unlike the energy needs, take into consideration equipment eﬃciency and conversion factors from the energy sources used.

Table 1. Main building areas of the case study in Porto, Portugal.

Building Average GHFA * Wall Area Roof North East South West GHFA * Footprint Per Person (Excl. Windows) Area Windows Windows Windows Windows 582 m2 1265 m2 20 m2 2712 m2 622 m2 0 m2 22 m2 0 m2 11 m2 * GHFA—gross heated ﬂoor area.

Table 2. Building energy parameters of the case study in Porto, Portugal.

Energy Parameters Unit Data

Typical indoor temperature (Heating/Cooling Season) ◦C 15/25 * U-value wall W/(m2.K) 0.96 U-value attic ﬂoor W/(m2.K) 0.91 U-value windows W/(m2.K) 3.60 g-value windows Factor 0.78 Energy needs for cooling kWh/(y.m2) 2.20 ** Energy needs for heating kWh/(y.m2) 53.36 ** Energy needs for hot water kWh/(y.m2) 29.60 ** Primary energy needed for cooling, heating and hot water kWh/ (y.m2) 177 ** Airﬂow rate ac/h 1.73 * * Average value obtained from a one year measurement campaign (2017); ** Simulated values.

The building envelope presents signs of deterioration, indicating a need for an immediate repair intervention. The common areas of the building (stairs, halls and walls) show evident signs of humidity and mold. Inside the apartments, thermal discomfort is common, and mold is clearly visible in the corners of the walls and near the windows. Extensive mold areas can also be found in some of the rooms and bathrooms ceilings. Some of the apartments have portable electrical heaters (η = 100%) although the majority does not have any heating system installed. In general, identiﬁed current renovation needs can be related to the correction of thermal bridges, the need to an increase of the insulation level and the installation of a heating system. Despite the importance of its representativeness, the building was chosen as a case study also because, within the scope of the More-Connect research project, there was the opportunity to assist in decision making in choosing the best renovation solution to implement.

3.2. Renovation Scenarios Deﬁnition

3.2.1. The More-Connect Renovation Solution The EU H2020 More-Connect research project (https://www.more-connect.eu/the-project/) aimed at developing cost-optimal solutions for deep renovations towards nZEB buildings. The project focused on the improvement of the energy performance of the building, through the development of prefabricated solutions for façades and roofs that can contribute to achieving the nZEB level. In the context of this research project, the University of Minho developed a prefabricated modular panel to improve the insulation level of the exterior walls of the existing building. The renovation solution comprises a wood frame, an internal/external cladding made of Coretech®sheets and a ﬁlling material of polyurethane foam (Figure3). Sustainability 2020, 12, 1631 7 of 17 Sustainability 2020, 12, x FOR PEER REVIEW 7 of 17

Figure 3. Prefabricated element for façade renovation: (1) Coretech® sheets, (2) Wood frame and (3) PolyurethaneFigure 3. Prefabricated foam. element for façade renovation: (1) Coretech® sheets, (2) Wood frame and (3) Polyurethane foam. During its development process, aspects such as reuse and recycling were considered to support the decisionDuring in its selecting development the most process, appropriate aspects materials such as forreuse each and prefabricated recycling were panel considered element. Regardingto support thethe frame decision structure, in selecting wood wasthe chosenmost appropriate for its high thermalmaterials performance, for each prefabricated allowing reducing panel thermalelement. bridges,Regarding particularly the frame in structure, the connection wood was between chosen modules. for its high Also, thermal at the endperformance, of the service allowing life, wood reducing can bethermal easily reusedbridges, for particularly secondary materialsin the connection or used in betw processeseen modules. of energy Also, recovery. at the In end the of external the service/internal life, ® claddingwood can of be the easily façade reused modules, for itsecondary was decided materials to use Coretechor used in thatprocesses is a material of energy manufactured recovery. In with the recyclingexternal/internal by-products cladding from theof the automotive façade modules, industry, it contributing, was decided this to use way, Coretech to reduce® that the exploitationis a material ofmanufactured raw materials with and recycling the amount by-pro of waste.ducts from In addition, the automotive it presents industry, attractive contributing, characteristics, this way, such to asreduce high durability,the exploitation water of and raw fire materials resistance, and asthe well amou asnt a lowof waste. U-value In addition, [29]. Several it presents alternatives attractive for thecharacteristics, insulation material, such as high including durability, bio-based water and materials, fire resistance, were assessed as well againstas a low aU-value set of criteria [29]. Several that includedalternatives the for ability the insulation to reuse and material, recycle including the material, bio-based but alsomaterials, the cost, were thickness assessed/e ffiagainstciency a ratio,set of weightcriteria and that material included availability the ability in the Portugueseto reuse context.and recycle For the the insulation material, of the but cavity also of thethe panel,cost, injectedthickness/efficiency polyurethane ratio, foam wasweight selected. and Thismaterial choice availability is strongly relatedin the toPortuguese its recognized context. high thermalFor the performanceinsulation ofand the highcavity durability of the panel, together injected with polyurethane considerable foam low weight.was selected. This choice is strongly relatedIn this to its project, recognized the developed high thermal panel isperformance to be applied and in thehigh existing durability building together with thewith dimensions considerable of 3 10.00low weight. m high and 2.40 m width. The panel, with a total thickness of 12 cm and a density of 19.70 kg/m , ® consistsIn this of two project, 1 cm the thick developed layers of panel Coretech is to be, aapplied 10 cm in thick the woodexisting frame building and with a 10 cmthe thickdimensions layer ofof polyurethane10.00 m high foam.and 2.40 The m assembly width. The between panel, thewith modules a total thickness is made ofof a12 male-female cm and a density connection of 19.70 in thekg/m wood3, consists frame. of For two a 1 correct cm thick and layers effective of Coretech application®, a of10 thecm panel,thick wood it was frame necessary and a to 10 create cm thick an interfacelayer of polyurethane between the existing foam. The building assembly wall between and the prefabricatedthe modules is element made of to a absorb male-female the irregularities connection ofin the the contacting wood frame. surfaces For a andcorrect ensure and continuouseffective application insulation. of For the this panel, interface, it was itnecessary was used to as create a layer an of mineral wool (MW) with a density of 25 kg/m3. A prototype of the module with 2.55 m 1.00 m interface between the existing building wall and the prefabricated element to absorb the irregularities× wasof the built contacting and tested surfaces at the Universityand ensure ofcontinuous Minho facilities. insulation. Thermal For this chamber interface, tests it indicated was used a as thermal a layer 2 transmittanceof mineral wool of 0.7 (MW) W/m wi.Kth The a density system of was 25 designedkg/m3. A toprototype be built oofff site,the module using an with industrial 2.55 m assembly × 1.00 m line,was inbuilt opposition and tested to the at layeredthe University manual of traditional Minho fa constructioncilities. Thermal techniques chamber usually tests appliedindicated in a Portugal. thermal Thetransmittance system will of be 0.7 produced W/m2.K The in disystemfferent was size designed modules to to be adapt built tooffsite, the di usingfferent an dimensionalindustrial assembly needs ofline, buildings. in opposition to the layered manual traditional construction techniques usually applied in Portugal. The system will be produced in different size modules to adapt to the different dimensional 3.2.2. Selection of Renovation Scenarios to be Analyzed needs of buildings. To achieve the objectives of the study, various energy renovation scenarios (envelope renovation package3.2.2. Selection plus systems of Renovation solutions) Scenarios were considered. to be Analyzed The renovation scenarios considered in the analysis have anTo emphasisachieve the on objectives the prefabricated of the study, modular various approach, energy but renovation include additional scenarios measures(envelope torenovation improve thepackage building plus envelope systems andsolutions) systems were solutions, considered providing. The heating,renovation cooling scenarios and renewableconsidered energy. in the Inanalysis addition have to an the emphasis prefabricated on the modular prefabricated solution, modular combinations approach, ofbut building include envelopeadditional measures measures (improvementto improve the of building the roof, envelope cellar ceiling and systems and windows) solutions, with providing building heating, systems, cooling take and into renewable account theenergy. common In addition use and applicabilityto the prefabricated in the national modula contextr solution, (Table combinations3). In the Portuguese of building context, envelope the replacementmeasures (improvement of windows isof a the very roof, common cellar renovationceiling and measure, windows) not with only building for its recognized systems, take benefits into regardingaccount the improved common thermal use and insulationapplicability and in thermal the national comfort, context but (Table also because 3). In the of Portuguese its contribution context, to achievingthe replacement a better acousticof windows environment is a very and common an increased renovation airtightness measure, in dwellings. not only Althoughfor its recognized detailed benefits regarding improved thermal insulation and thermal comfort, but also because of its contribution to achieving a better acoustic environment and an increased airtightness in dwellings. Sustainability 2020, 12, 1631 8 of 17 considerations regarding airtightness are out of the scope of this study, it is worth mentioning that the replacement of the windows did not lead to a significant decrease of the airflow rates, which is consistent with the results found in other studies (e.g., [30]). In addition, it should also be highlighted that the airtightness resulting from the renovation measures considered in this study complies with the minimum requirements determined by the Portuguese legislation in what concerns the indoor air quality in both winter and summer periods.

Table 3. Proposed envelope renovation packages for the pilot building.

Renovation Description Package The walls are repaired and painted, and the pitched roof is refurbished (with new tiles). These measures do not Reference improve the energy performance of the building M1 The walls are insulated with ETICS—8 cm EPS 1 M2 The walls are insulated with a prefabricated element (12 cm) and 6 cm MW 2 layer M3 The walls are insulated with a prefabricated element (12 cm) and 10 cm MW layer M4 M3 plus the refurbishment of the roof (including membrane), roof battens, shuttering, gutter and a 6 cm MW layer M5 M3 plus the refurbishment of the roof (including membrane), roof battens, shuttering, gutter and a 12 cm MW layer M6 M3 plus the refurbishment of the roof (including membrane), roof battens, shuttering, gutter and a 14 cm MW layer M7 M6 plus the cellar ceiling is insulated with 6 cm MW layer 2 M8 M7 plus the new windows (aluminum frame and a U-value of 2.70 W/m ◦C) 2 M9 M7 plus the new windows (aluminum frame and a U-value of 2.40 W/m ◦C) M10 M9 plus a solar thermal system is installed M3 plus the refurbishment of roof with 6 cm of polyurethane (including membrane) roof battens, shuttering, and M11 gutter. The cellar ceiling refurbished—6 cm XPS 3 M12 M11 with optimized costs for the production of the prefabricated element 1 EPS—expanded polystyrene; 2 MW—mineral wool; 3 XPS—extruded polystyrene.

The first renovation package (Reference) comprises the reference situation from which the cost-effectiveness is going to be evaluated, as explained in Reference [24], and shown in Figure1. The renovation package M1 comprises the application of an 8 cm thick layer of expanded polystyrene (EPS) in an external thermal insulation composite system (ETICS). This solution is the most common solution used in building energy renovation in Portugal, and it has already been identified in another study [30] as being the cost-optimal solution for the envelope of this kind of buildings. The subsequent renovation packages (from M2 to M11) explore different insulation thicknesses and progressively test new levels of intervention for the building renovation. The last renovation package (M12) intends to explore the effect of future optimization of the prefabricated panel production costs. Currently, the developed modular prefabricated panel has very high investment costs because it does not yet have an optimized assembly line designed for mass production. According to calculations led by the manufacturing company participating in the More-Connect project, while taking into account the Portuguese industrial context, improvements in the production process, as well as economies of scale derived from mass production, would originate a reduction of 70% in the production costs. In terms of systems, Table4 shows the di fferent systems solutions considered in this study in terms of heating, cooling, Domestic Hot Water (DHW) and Renewable Energy Sources (RES). The systems shown in Table4 are in line with the multitude of implemented options found in the Portuguese context and include innovative solutions regarding the use of renewable energy sources, with high potential for energy and emissions reduction. The conventional system solution (electric heater for heating, multisplit system for cooling and gas heater for DHW) is the default solution to be considered in the existing building before the intervention as mentioned by the Portuguese legislation [19]. In system solution D, the photovoltaic contribution consists of an installation with a peak power capacity of 7.50 kWp. The sizing of this contribution was calculated to compensate for theoretical heating needs. In system solution F, the photovoltaic contribution consists of an installation with the necessary capacity to compensate the energy needs fully. Similarly, in system solution G, the size of the photovoltaic system is adequate to compensate the heating and cooling needs, whereas, Sustainability 2020, 12, 1631 9 of 17 domestic hot water (DHW) is supported by a solar thermal installation, sized according to the minimum requirements of the Portuguese legislation.

Table 4. Proposed systems solutions for the building.

System Solution Heating Cooling DHW RES Conventional Electric heater η = 1 Multisplit EER = 3 Gas heater η = 0.71 A Multisplit COP = 4.1 Multisplit EER = 3.5 Gas heater η = 0.71 B Gas boiler η = 0.93 Multisplit EER = 3.5 Gas boiler η = 0.93 C Biomass boiler η = 0.92 Multisplit EER = 3.5 Biomass boiler η = 0.92 D Heat Pump COP = 3.33 Heat pump EER = 2.68 Heat Pump COP = 3.33 PV 1 (7.5 kWp) E Heat Pump COP = 3.33 Heat pump EER = 2.68 Heat Pump COP = 3.33 F Heat Pump COP = 3.33 Heat pump EER = 2.68 Heat Pump COP = 3.33 PV (Zero) 2 G Multisplit COP = 4.1 Multisplit EER = 3.5 Electric Boiler COP 1.5 PV (Zero) ST 3 for DHW 1 PV—Photovoltaic; 2 PV (Zero)—Photovoltaic contribution consists of an installation with the necessary capacity to fully compensate the energy needs for heating and cooling; 3 Solar Thermal (ST)—Solar Thermal contribution consists of an installation, sized according to the minimum requirements of the Portuguese legislation.

After an overall analysis, due to budget constraints and material availability, the building owner selected the renovation package M11 and system solution C as the measures to be implemented in the renovated building. To assess the performance of this very specific option, the Selected System Combination (SSC), shown in Table5, was calculated, and the results are shown in the next section. The system solution in this combination (Table5) is identical to system solution C without the system to deal with the cooling needs. The Portuguese thermal regulation [19] allows this simplification whenever the overheating risk in summer is minimum, which is quite common in a substantial part of the Portuguese territory. There is an expeditious method to evaluate the risks of overheating, which is to calculate the heat gains utilization factor that depends on the thermal mass and on balance between heat gains and heat losses throughout the building envelope. When this factor is higher than the reference value (which is true in the building under analysis), the overheating risk is non-existent, and the cooling needs are not accounted for in the calculated energy needs. This is a very common situation in existing Portuguese buildings, due not only to specific climate conditions, but also to significant heat losses and medium to high thermal mass that characterizes a significant number of residential buildings in Portugal. In accordance with the national thermal regulations, the analysis performed in this study only calculated the non-renewable primary energy (NRPE) share of the total primary energy and the respective emissions.

Table 5. Renovation package and system solution for the Selected System Combination to be implemented in the renovated building.

Renovation Package System Solution Heating Cooling DHW M11 (M12 1) Biomass boiler η = 0.92 _ Biomass boiler η = 0.92 1 M12 corresponds to M11 with optimized production costs of the prefabricated panel.

4. Results and Discussion

4.1. Cost-eﬀectiveness of Renovation Packages Figure4 shows the results in terms of global costs ( €/m2) and NRPE—Non-Renewable Primary Energy (kW.hEP/(y.m2) of the combinations considered in the calculations between the twelve renovation packages (Table3), the eight systems solutions (Table4) and the selected system combination (Table5). In Figure4, the results are presented, not considering the embodied energy of the materials used in the renovation. Sustainability 2020, 12, x FOR PEER REVIEW 10 of 17

Table 5. Renovation package and system solution for the Selected System Combination to be implemented in the renovated building.

4. Results and Discussion

4.1. Cost-effectiveness of Renovation Packages

Figure 4 shows the results in terms of global costs (€/m2) and NRPE—Non-Renewable Primary Energy (kW.hEP/(y.m2) of the combinations considered in the calculations between the twelve renovation packages (Table 3), the eight systems solutions (Table 4) and the selected system Sustainabilitycombination2020, 12, 1631 (Table 5). In Figure 4, the results are presented, not considering the embodied energy of 10 of 17 the materials used in the renovation.

Figure 4.FigureCost-optimal 4. Cost-optimal results forresults the analyzedfor the analyzed renovation renovation packages packages without without considering considering the embodiedthe embodied energy of the materials used in the renovation. energy of the materials used in the renovation.

4.2. Cost-e4.2.ffectiveness Cost-effectiveness of Renovation of Renovation Packages Packages Per Per System System SolutionSolution To compare the effect of embodied energy and carbon emissions in the cost-effectiveness of To comparerenovation thescenarios, effect Figures of embodied 5–12 present energy the calc andulation carbon results emissions for renovation in thepackages cost-e perffectiveness system of renovationsolution scenarios, with and Figures without5–12 considering present the the calculation embodied energy results of for the renovation materials in packages terms of global per system solutionwarming with and potential without represented considering by carbon the embodied emissions (kg.CO energy2eq/(y.m of the2)) materialsand cumulative in terms primary of global 2 2 warmingenergy potential (kW.h/(y.m represented)) per year. by carbon In the graphs, emissions maximum (kg.CO differ2eqence/(y.m (in)) red) and and cumulative minimum primarydifference energy (kW.h/(y.m(in2 green))) per year.in indicators In the considering graphs, maximum results with diff anderence without (inred) the embodied and minimum energy diandfference emissions (in green) parcel are highlighted in color and by indicating the measure number. The results are presented, in indicators considering results with and without the embodied energy and emissions parcel are taking into consideration annualized costs (€/(y.m2)). highlighted in color and by indicating the measure number. The results are presented, taking into consideration annualized costs (€/(y.m2)).

(a) (b)

Figure 5. System solution—Conventional: (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2: MC panel 12 cm + 6 cm, M3: MC panel + 10Figure cm, M4:5 M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

(a) (b)

Figure 6

(a) (b)

Sustainability 2020, 12, 1631 Figure 5 11 of 17

(a) (b)

Figure 6. System solution A—Multisplit (heating/cooling) + Gas heater (DHW): (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2:Figure MCpanel 6 12 cm + 6 cm, M3: MC panel + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 1 4cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

(a) (b)

Figure 7. System solution B—Multisplit (cooling) + Gas boiler (heating/DHW): (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2:Figure MC panel 7 12 cm + 6 cm, M3: MC panel + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

(a) (b)

Figure 8

(a) (b)

Sustainability 2020, 12, 1631 Figure 7 12 of 17

(a) (b)

Figure 8. System solution C—Multisplit (cooling) + Biomass boiler (heating/DHW): (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2: MCFigure panel 8 12cm + 6 cm, M3: MC panel + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows

2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization, SSC: Selected System Combination.

(a) (b)

Figure 9. System solution D—Heat Pump + PV system: (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2: MC panel 12 cm + 6 cm, M3:Figure MC panel 9 + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

Overall, in terms of non-renewable primary energy and CO2 emissions (Figures5–12), the renovation package M10 leads to the lowest energy consumption (in average 22.6 kWh/(y.m2)), as well 2 as to the lowest CO2 emissions (in average 3.6 kgCO2eq/(y.m )). The renovation package M10 (M9 + solar thermal) includes the modular prefabricated panel together with a 10 cm layer of mineral wool applied in the interface between the panel and the existing wall, a 14 cm layer of mineral wool on the roof and a 6 cm layer of extruded polystyrene in the cellar ceiling. For the windows, the solution for package M10 includes the replacement of the windows by others with an aluminum frame and a 2 U-value of 2.40 W/m ◦C.

(a) (b)

Figure 10

(a) (b)

Sustainability 2020, 12, 1631 Figure 9 13 of 17

(a) (b)

Figure 10. System solution E—Heat Pump: (a) Emissions (b) Primary energy. Where: M1: ETICS 8 cm, M2: MC panel 12 cm + 6 cm, M3: MC panel +Figure10 cm, 10 M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

3 (a) (b)

Figure 11. System solution F—heat pump + PV system towards zero: (a) Emissions (b) Primary energy. Figure 11 Where: M1: ETICS 8 cm, M2: MC panel 12 cm + 6 cm, M3: MC panel + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

The results of the calculations indicate that the solutions considering heat pump systems (systems solutions D, E and F) lead to significant reductions in the two analyzed indicators. System solution F is a clear example, where a 90% reduction in NPRE can be achieved when compared with the reference case. However, achieving these reductions with such systems are still above the limit of cost-effectiveness. In relation to global costs, the more evident increase is in the system solution E (Figure 10) where the global costs are 39.9% (M6) higher than the costs related to the reference case. This system is composed of a heat pump for heating, cooling and DHW. Results suggest that under system solution G (Figure 12), every renovation package is cost-effective. With this system, there is an NRPE reduction of around 83.5% when compared with the reference case, while the global costs range from being 8% (M10) to 33.7% (M12) smaller than the ones related to the

(a) (b)

Figure 12

Sustainability 2020, 12, 1631 14 of 17 (a) (b) reference case. This system includes a multisplit equipment for heating and cooling, an electric boiler Figure 11 for DHW, in addition to photovoltaic and solar thermal panels.

(a) (b)

Figure 12. System solution G—Multisplit + Electric Boiler (DHW) + PV system towards zero + ST: (a) Emissions (b) Primary energy. Where: M1: ETICSFigure 8 12 cm, M2: MC panel 12 cm + 6 cm, M3: MC panel + 10 cm, M4: M3 + Roof 6 cm, M5: M3 + Roof 12 cm, M6: M3 + Roof 14 cm, M7: M6 + Cellar 6 cm, M8: M7 + Windows 2.7, M9: M7 + Windows 2.4, M10: M9 + ST, M11: M3 + Roof 6 cm + Cellar 6 cm, M12: M11 + cost optimization.

In terms of renovation packages, and taking into account the calculated annualized costs (Figures5–12), the renovation package M12 is the one that leads to the lowest global costs regardless of the system solution considered. This renovation package considers cost optimization of the prefabricated modular panel, combined with roof and cellar insulation. When the optimization of the panel is not considered, the renovation package M1 leads to the lowest global costs in all system solutions, except in system solution C, where M11 leads to the lowest global costs. The Selected System Combination (SSC) is the cost-optimal solution (Figures4 and8). Although not initially considered in the renovation solutions analyzed in this study, it is the solution that the building owner will be able to implement, due to technical, ﬁnancial and material availability reasons, and was therefore, calculated as a separate combination. The SSC includes the (cost optimized) prefabricated modular panel (M12) together with a biomass boiler. This renovation solution leads to a reduction of 226 kWh/(y.m2) when compared with the reference case, at a global cost of 34 €/(y.m2). This combination uses only a renewable energy source4 (wood) for both acclimatization and DHW.

Inﬂuence of Embodied Energy and Embodied Carbon Emissions When the embodied carbon emissions and embodied energy of the materials used are considered in the calculations, there is a noticeable increase in the cumulative primary energy and in the global warming potential in terms of carbons emissions per year of each renovation package, regardless of 2 the system solution used. Generically, carbon emissions increase in average by 9.3 kgCO2eq/(y.m ) and primary energy by 43 kWh/(y.m2). The cost-optimal solution for the envelope is the renovation package M12 (M11 with optimization of the panel cost production) considering or not the embodied energy in the materials. However, with this renovation package, when embodied energy and emissions are considered, there is an 2 2 average increase of 45.3 kWh/(y.m )) in primary energy and 10.3 kgCO2eq/(y.m )) in emissions per year. The renovation package that leads to the lowest increase in carbon emissions and primary energy 2 2 (4.1 kgCO2eq/(y.m ) and 15.6 kWh/(y.m )) is M1 (ETICS EPS 8 cm), when system solution F is considered. Sustainability 2020, 12, 1631 15 of 17

The highest increase in primary energy (120.5 kWh/(y.m2)) is found when renovation package M2 (Modular Panel+6 cm insulation) is considered together with system solution C (biomass boiler + 2 Multisplit). Regarding carbon emissions, the highest increase (18.1 kgCO2eq/(y.m )) is found with the application of the same measure, but when the conventional system (electric heater + multisplit+ gas heater) is used in calculations. In fact, concerning systems solutions, the consideration in the calculations of the embodied energy and embodied carbon emissions of the materials lead to some changes and a significant increase in the values of primary energy and carbon emissions associated to the renovation scenarios, particularly in scenarios that include renewable energy sources. The most notable changes were observed in the combination of system solution C (multisplit + biomass boiler) with the different renovation packages. For this system solution, and regarding carbon emissions 2 2 and primary energy, the values increase by an average of 9.4 kgCO2eq/(y.m ) and 109 kWh/(y.m ), respectively. System solution F (heat pump + PV) also leads to significantly higher values of carbon 2 2 emissions (6.7 kgCO2eq/(y.m ) in average) and primary energy (27.5 kWh/(y.m ) in average), which is clearly associated to the size of the photovoltaic system. Finally, it is important to refer that, despite the observed increase of these values, in general terms, the hierarchical relationship between combinations of system solutions and renovation packages remain identical, as well as the comparative position of the renovation packages in relation to the reference situation. In this case, not only the cost-optimal solution remains the same when the embodied energy is considered, but also the cost-effectiveness of the measures remains mostly unchanged.

5. Conclusions Based on the assessment carried out it is possible to conclude that for the building envelope, the renovation package that consistently allows for the highest reduction of the energy needs in all renovation scenarios (86% in average) is M10 (M9 + solar thermal). This solution leads to a significant reduction of the energy needs and CO2 emissions, but it is not very attractive in terms of costs. The cost-optimal renovation package is M12, which includes the modular panel, as well as roof and cellar insulation. This package assumes that the production costs of the panel are already optimized, and a production cost reduction of 70% was achieved. Regarding the systems, the one allowing for a more significant reduction (up to 226 kWh/(y.m2)) is the Selected System Combination, which considers a biomass boiler and no cooling equipment. Calculations results considering the System Solution C, which also uses a biomass boiler combined with a multisplit, show relevant results in terms of primary energy and carbon emissions reduction. In addition, system solution F allows reducing the primary energy and carbon emissions above 80%, but at a higher cost. The consideration in the calculations of the embodied carbon emissions and the embodied energy of the materials used increases the energy and carbon emissions of each renovation package by an 2 2 average of 43 kWh/(y.m ) and 9.3 kgCO2eq/(y.m ), respectively in all renovation scenarios. However, in general terms, the relationship between combinations of system solutions and renovation packages remain identical. When LCA results are integrated into the cost-optimal calculations, renovation package M12 is still the cost-optimal solution. Although it is not leading to the most significant primary energy reduction, renovation package M1, with system solution F, is the one leading to the lowest increase in embodied carbon emissions and primary energy. Results suggest that prefabricated modular systems present advantages regarding primary energy and carbon emissions reductions, but caution should be exercised in the choice of materials to reduce associated embodied energy and carbon emissions. In this case, results show that the choice of polyurethane foam harmed the overall performance regarding the environmental impact of the prefabricated modular panel. In that way, another type of materials should also be considered in future analysis. In this context, and since the module is composed of different elements with distinctive life cycles, another topic to be considered in future works concerns the assessment of circularity of the components of the prefabricated modular panel. Sustainability 2020, 12, 1631 16 of 17

In addition, the results also show that, while renewable energy supply systems may be beneficial in terms of reductions in non-renewable primary energy use, embodied energy and life cycle implicit emissions associated to the materials and processes used in the renovation process can hinder the sustainability of these measures. In this sense, future research will have to include the further development of both prefabricated modular renovation solutions and renewable energy sources with reduced embodied energy and carbon emissions to improve the sustainability of the cost-effective and affordable building renovation interventions.

Author Contributions: Supervision, M.A.; Conceptualization, M.A. and R.B.; methodology, M.A.; investigation, M.A. and R.B. formal analysis, M.A. and R.B.; visualization, R.M.; writing—original draft preparation, R.M. and R.B.; writing—review and editing, R.B. and M.A. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by European Union’s H2020 framework programme for research and innovation project “Development and advanced prefabrication of innovative, multifunctional building envelope elements for MOdular REtrofitting and CONNECTions” under grant agreement no 633477. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Peter, C.; Swilling, M. Sustainable, Resource Efficient Cities-Making it Happen; United Nations Environment Programme: Nairobi, Kenya, 2012; ISBN 978-92-807-3270-2. 2. OECD. Environment at a Glance 2015: OECD Indicators; OECD Publish: Paris, France, 2015. 3. Gynther, L.; Lapillone, B.; Pollier, K. Energy Efficiency Trends and Policies in the Household and Tertiary Sectors. In An Analysis Based on the ODYSSEE and MURE Databases; European Union: Brussels, Belgium, 2015. 4. European Commission. A Clean Planet for all A European Strategic Long-Term Vision for a Prosperous, Modern, Competitive and Climate Neutral Economy; EC: Brussels, Belgium, 2018. 5. European Commission 2030 Climate & Energy Framework. Available online: https://ec.europa.eu/clima/ policies/strategies/2030_en (accessed on 12 October 2018). 6. Recast, E.P.B.D. Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast). Off. J. Eur. Union 2010, 18, 13. 7. Almeida, M.; Ferreira, M. IEA EBC Annex56 vision for cost effective energy and carbon emissions optimization in building renovation. Energy Procedia 2015, 78, 2409–2414. [CrossRef] 8. Artola, I.; Rademaekers, K.; Williams, R.; Yearwood, J. Boosting Building Renovation: What potential and value for Europe. In Study for the ITRE Committee, Commissioned by DG for Internal Policies Policy Department A; European Parliament: Brussels, Belgium, 2016; ISBN 978-92-846-0308-4. 9. D’Oca, S.; Ferrante, A.; Ferrer, C.; Pernetti, R.; Gralka, A.; Sebastian, R.; Veld, P. Technical, financial, and social barriers and challenges in deep building renovation: Integration of lessons learned from the H2020 cluster projects. Buildings 2018, 8, 174. [CrossRef] 10. Copiello, S. Achieving affordable housing through energy efficiency strategy. Energy Policy 2015, 85, 288–298. [CrossRef] 11. Hochstenbach, C.; Musterd, S. Gentrification and the suburbanization of poverty: Changing urban geographies through boom and bust periods. Urban Geogr. 2018, 39, 26–53. [CrossRef] 12. Pérez-Fargallo, A.; Rubio-Bellido, C.; Pulido-Arcas, J.A.; Javier Guevara-García, F. Fuel Poverty Potential Risk Index in the context of climate change in Chile. Energy Policy 2018, 113, 157–170. [CrossRef] 13. Almeida, M.; Barbosa, R. The More-Connect: Concepts of renovations packages. In A Guide into Renovation Package Concepts for Mass Retrofit of Different Types of Buildings with Prefabricated Elements for (n)ZEB Performance; Huygen/RiBuilT-SBS/Zuyd: Herleen, The Netherlands, 2018; ISBN 978-9934-22-209-2. 14. Hejtmánek, P.; Volf, M.; Sojková, K.; Brandejs, R.; Kabrhel, M.; Bejˇcek,M.; Novák, E.; Lupíšek, A. First Stepping Stones of Alternative Refurbishment Modular System Leading to Zero Energy Buildings. Energy Procedia 2017, 111, 121–130. [CrossRef] 15. Almeida, M.; Ferreira, M.; Barbosa, R. Relevance of Embodied Energy and Carbon Emissions on Assessing Cost Effectiveness in Building Renovation—Contribution from the Analysis of Case Studies in Six European Countries. Buildings 2018, 8, 103. [CrossRef] Sustainability 2020, 12, 1631 17 of 17

16. Lasvaux, S.; Favre, D.; Périsset, B.; Mahroua, S.; Citherlet, S. Life Cycle Assessment for Cost-Effective Energy and Carbon Emissions Optimization in Building Renovation (Annex 56); University of Minho: Braga, Portugal, 2017. 17. Lützkendorf, T.; Foliente, G.; Balouktsi, M.; Houlihan Wiberg, A.; Lu tzkendorf, T. Net-zero buildings: Incorporating embodied impacts Net-zero buildings: Incorporating embodied impacts. Build. Res. Inf. 2014, 43, 62–81. [CrossRef] 18. EU Commission. Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012 Supplementing Directive 2010/31/EU of the European Parliament and of the Council on the Energy Performance of Buildings. Off. J. Eur. Union 2012, 55, 18–36. 19. República Portuguesa. Decreto-Lei n.o 118/2013—Regulamento de Desempenho Energético dos Edifícios de Habitação (REH). Diário da República 1.a série N.o 2013, 159, 4988–5005. 20. DGEG SCE.ER—Software for Definition of Minimum Requirements and Regulation Verification for Renewable Energy Supply Systems. Available online: http://www.dgeg.gov.pt/ (accessed on 14 November 2019). 21. European Commission. JRC Photovoltaic Geographical Information System (PVGIS)—European Commission. Available online: https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html (accessed on 14 November 2019). 22. CYPE Ingenieros, S.A. Gerador de Preços. Portugal. Available online: http://www.geradordeprecos.info/ (accessed on 14 November 2018). 23. More-Connect. Available online: https://www.more-connect.eu/ (accessed on 14 November 2019). 24. Ferreira, M.; Almeida, M.; Rodrigues, A.; Silva, S.M. Comparing cost-optimal and net-zero energy targets in building retrofit) Comparing cost-optimal and net-zero energy targets in building retrofit Comparing cost-optimal and net-zero energy targets in building retro¢t. Build. Res. Inf. 2016, 44, 188–201. [CrossRef] 25. CSN. Sustainability of construction works—Assessment of environmental performance of buildings— Calculation method. In European Standards; BSI BS EN 15978: 2011; European Committee for Standardization: Brussels, Belgium, 2011. 26. Bragança, L.; Mateus, R. Life-Cycle Analysis of Buildings: Environmental Impact of Building Elements; Associação iiSBE Portugal: Guimarães, Portugal, 2012; ISBN 978-989-96543-3-4. 27. INE. O Parque Habitacional e a sua Reabilitação—Análise e Evolução 2001–2011; Instituto Nacional de Estatistica: Lisboa, Portugal, 2011; ISBN 9789892502465. 28. Climate-Data.org—Vila Nova de Gaia Climate. Available online: https://en.climate-data.org/europe/portugal/ vila-nova-de-gaia/vila-nova-de-gaia-718503/ (accessed on 15 November 2019). 29. Coretech Portugal. Available online: https://www.coretech.com.pt/ (accessed on 14 November 2019). 30. Oreszczyn, T.; Mumovic, D.; Ridley,I.; Davies, M. The Reduction in Air Infiltration due to Window Replacement in UK Dwellings: Results of a Field Study and Telephone Survey. Int. J. Vent. 2005, 4, 71–77. [CrossRef]

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).